Loosely remixed from Parametric Spool Hub by hdonk http://www.thingiverse.com/thing:28046.

The primary reason for the remix was to correct issues with the mesh between the spokes and the hub. Provisions have been added to chamfer the edges that insert into the filament spool, and the number of cylinder facets is now factored from the diameter of the adapter.

For ease of use and tailoring by others, the openSCAD script has also been extensively commented.

The STL provided is just a sample output, rendering a spool adapter 52mm diameter with an axle hole of 8mm. Other sizes are possible through changes to the parameter definitions in the openSCAD script. The gallery picture also just shows some of the variations of spool adapters created with the script.